1. Field of the Invention
The present invention relates to a keypad assembly having keycaps, and an image forming device and a data processor incorporating the same.
2. Description of the Prior Art
An image forming device such as a copier includes an operation panel through which a user gives an instruction to the device. The operation panel includes a key operation unit to which numeric values such as the number of copies or prints, facsimile numbers and else are input. Japanese Patent Application Publication No. 11-167457 (Reference 1) discloses a key operation unit with a keypad assembly of keycaps having keyswitches and extensions and keycaps not having keyswitches so that upon press to a certain keycap, the extensions of neighboring keycaps overlapping with the certain keycap are also pressed down to press the keyswitches, for example.
Japanese Patent No. 4089118 (Reference 2) discloses a keypad assembly which includes a first keypad element in which keycaps are arranged via an elastic arm element in a frame on which support portions vertically stand, and a second keypad element in which a single keycap is disposed at the center of a frame on which support portions vertically stand via an elastic arm element. The first keypad element is placed on the second keypad element and assembled into a device body.
Such a keypad assembly having partially overlapped keycaps or keypad elements can reduce its size and manufacturing costs. However, it has a drawback that it is applicable to composite keys such as cursor keys consisting of a center key and four surrounding keys or arrow keys tightly arranged without a gap but not applicable to a keypad structure such as a numerical keypad of keycaps in the same size and shape arranged vertically and horizontally with a constant interval. In particular, the keypad assembly in Reference 2 includes differently shaped elastic arms for the center keycap and the surrounding keycaps so that there are differences in key touches and key durability due to a difference in elastic force. Therefore, it is not suitable for a numerical keypad having the same size and function.